This invention relates to a weighing system that is used by placing a pair of scales under the legs or wheels of an object such as a bed, chair, chaise lounge, sofa or the like. The weighing system has improved accuracy and stability over other such systems and may be used to determine the weight of patients in a plurality of types of hospital beds, nursing home beds, chairs, or for home use.
It is frequently desirable to accurately monitor the weight of a patient confined to a bed, chair, etc., whether in a hospital, in a nursing home, at home, or in other treatment settings, and to observe changes in weight to monitor the health of the patient and ensure that proper dosages of medication are administered. It is difficult, however, to weigh seriously ill patients or persons with limited mobility by removing them from the bed on a regular basis. Critically ill patients, in particular, may require frequent weighing, with their severe physical condition preventing their removal from bed.
The current method of determining the weight of a patient in a hospital or nursing home bed is both time consuming and onerous. Additionally it involves some risk of danger both to the patient (possible spills, etc.) as well as the caregivers (back strain, etc.).
Typically two trained persons are needed to accomplish this task. Most often they will utilize a patient lift (or hoist) that has an attached scale. First, the patient is placed into a sling and harness assembly and then the sling is attached to the hoist, which has been centered above the bed. Utilizing the hoist, the patient is then raised approximately 12 inches above the bed so that his or her legs float free. The patient""s weight is then recorded and the patient is lowered back into the bed. An alternative to the above method is to simply bring a wheelchair to the bedside, transfer the patient from the bed to the wheelchair, and then wheel the chair to an appropriate scale. Unfortunately, the alternative is seldom possible. Patients in hospitals or nursing care facilities are there by Doctor""s orders. They are there because of the high level of care they need. They are seldom able or physically ready to transfer out of their bed to a wheelchair. They are typically disabled and often fragile following surgery. They may, and often do, become distressed when being transferred out of bed just to get their weight recorded.
Therefore, it is desirable to have a weigh system that is not time consuming for the caregiver, does not require two persons, and does not pose a risk or danger to either the patient or the caregiver.
Beds incorporating weighing systems, such that the patient need not be removed from the bed to be weighed, have been disclosed. For example, in Reichow et al. U.S. Pat. No. 5,269,388 and Carruth et al., U.S. Pat. No. 4,926,951. The system disclosed in Reichow et al. utilizes load cells, which are rigidly mounted along the sides of the bed frame. The Carruth system utilizes a separate weigh frame mounted to the bed frame. These systems are generally an integral part of the bed, and must be incorporated into the bed when it is manufactured. Beds incorporating these weighing systems are generally more expensive than ordinary beds without a weighing system, are typically permanently attached, and are also much heavier, making it more difficult to move such beds.
Therefore, it is desirable to have a weigh system that is not permanently attached to a hospital bed or nursing home bed, since it is necessary in such systems to have a complete system for each bed. In facilities having many beds, the cost of separate weigh facilities for each bed is substantial. Particularly in nursing home and extended care facilities it is frequently not necessary to check a patient""s weight every day, and having a portable system which may easily be used on various beds in the care facility at various times would be a substantial cost savings. In many installations, a single set of weighing devices may suffice for the entire facility.
U.S. Pat. No. 4,281,730, issued to Swersey et al, discloses the use of a portable under bed scale that can be used in pairs to determine the weight of a person in the bed. The invention disclosed in the Swersey patent determines the weight of a patient by measuring the displacement at the end of a pair of beams that are pivotally mounted to each scale. Springs are provided to return the beam ends to a non-displaced position after the weight has been removed.
The scale disclosed in the Swersey Patent, while portable still has several drawbacks. The Swersey Patent teaches that the maximum patient weight that can be accommodated is 150 kilograms (about 330 pounds) and the scale requires leveling. The Swersey Patent teaches the use of additional springs to provide accuracy and to reduce hysteresis, however hysteresis will still occur and the scale will have to be re-calibrated.
The Swersey Patent teaches that when a load is in place on the scales, the springs are under tension, and the beams xe2x80x9cfloat.xe2x80x9d This could potentially cause stability problems if a patient is not centered on the surface of the bed. If a patient suddenly moves, or is lying to one side of the bed, the bed could possibly tilt. Unfortunately, even a minor tilt of a hospital or nursing home bed could put the patient into an extreme risk of rolling out of the bed. Additionally, the Swersey patent does not disclose or address the common problem of inconsistent or inaccurate measurements caused by a patient""s position on the surface of the bed.
Therefore it is also desirable to have a totally portable weigh system that is stable and consistently accurate. Such a system should be adjustable to fit a plurality of objects that could hold a patient, and it must be capable of weighing relatively heavy patients. Such a system that does not require leveling and is relatively maintenance free and totally portable would be a significant advancement over the prior art.
Accordingly it is an objective of the present invention to provide a load cell weighing system, particularly useful in the accurate and reproducible measurement of the weight of an occupant in a hospital or nursing home bed, that may be conveniently used with a plurality of such beds without permanently attaching the system to such beds.
It is another objective of this invention to provide such a weighing system that is stable while in use so as to minimize the potential for patient injury due to the bed tilting.
It is a further objective of this invention to provide such a system that gives a consistently accurate weight regardless of a patient""s position on the surface of the bed.
Yet another objective of this invention is to provide such a system that is capable of weighing relatively heavy patients.
Another objective of this invention is to provide such a system that does not require leveling before use.
It is also an objective of this invention to provide such a system that requires relatively little maintenance, such as re-calibration.
Still another objective of this invention is to provide such a system that is relatively inexpensive, not time consuming for the caregivers, does not require two persons to operate it, and does not pose a risk or danger to either the patient or caregiver.
These and other such objectives as will become apparent from the disclosure below are met by the invention described herein.
A preferred embodiment of this invention includes two custom designed electronic load cell scales and one weight data collector. One custom designed electronic scale is placed under the two legs at the head of the bed and the other is placed under the two legs at the foot of the bed. Each of the scales comprise a beam shaped load cell with a stable floor engaging base, a support bar mounted above and attached to the load cell, and a pair of support bar extensions that are adjustably attached to the support bar so the scales can accommodate beds of different widths. The support bar extensions include a leg pad and a wheel cup to accommodate beds with different types of wheels or legs.
Weighing error is minimized by the use of electronic strain gauges that measure deflection in the beam shaped load cells. The electronic output of both load cells is conducted to a weight data collector where the total weight measured by the two load cells is calculated.
Due to the use of a deflectable beam shaped load cell, non-vertical, off center, or side directed force components can not introduce a weighing error into the system. As a result, the weighing system of this invention provides an accurate weight regardless of the patient""s position in or on the bed.
The weighing system of this invention is advantageously designed to accommodate a maximum weight of up to 750 pounds. The scales of this invention will not tip or tilt if a patient shifts his or her weight to one side, or the other, of the bed. The scales of this invention do not require leveling and they have no moving parts. They are therefore relatively maintenance free and require no re-calibration.
The weighing system of this invention teaches the use of two portable scales, and a weight data collector. The scales of this invention are adjustable to accommodate beds of various widths having various types of wheels or legs. In use, the scales are adjusted to the proper width for the bed to be accommodated. The load cells are then connected by wire to the weight data collector, and the bed is placed on the scales, one scale at the head of the bed and one scale at the foot of the bed. The electronic strain gauges in the load cells then measure the deflection of the beam type load cell and transmit the data to the weight data collector. The weight data collector calculates the weight and displays it on a digital readout.
Bed jacking devices can be used to place the bed on the scales, however this is not required. The weight data collector can be readily programmed to automatically subtract the weight of the bed before displaying the patient""s weight on the digital readout. The components of the scale are made of material sufficiently strong to support the weight of a patient up to 750 pounds plus the weight of the bed.
One example of an additional use for this system is in home health care. Often, people requiring some type of supervised health care prefer to remain in their homes. Sometimes, it is necessary to monitor the weight of a bed-ridden patient who is receiving such care in his or her home. Renting, transporting, and moving a bed with a weighing system permanently attached into a persons home could be expensive and difficult. To overcome these obstacles, the weigh system of this invention could be rented from a medical supply company, and placed under the patient""s existing bed. The supervising health care professional can then monitor the patient""s weight. When the scale is no longer needed, it simply can be returned to the medical supply company.
This invention provides a load cell weighing system, particularly useful in the accurate and reproducible measurement of weight of the occupant of hospital or nursing home beds. The weighing system of this invention may be conveniently used with a plurality of such beds without attaching the system to such beds. The scales of this invention are stable so as to minimize the potential for patient injury due to the bed tilting. The weighing system of this invention gives a consistently accurate weight regardless of a patient""s position on the surface of the bed, and is also capable of providing extremely accurate weight measurements for the relatively heavy patients. The weighing system does not require leveling before use and requires relatively little maintenance, such as re-calibration.